Complex electrical wiring networks, often having “branched circuits”, are extremely common in aircraft, ships, trains, large refineries and factories, homes, electronic equipment, etc. Often these wiring networks are installed and expected to work for the lifetime of the building or vehicle. The wiring networks are tested only if they no longer work. There is currently a lack of an effective, small and efficient sensor to precisely detect and locate electrical faults in a wiring network. The manpower and time required to manually check large and complex wiring networks can be considerable. In critical systems, such as aircraft, there is a need to detect and locate faults before a wiring network decays to the point of failure.
In the past few years there has been significant effort to develop sensors for locating wiring faults. Several sensor methods were developed that can locate the faults in dead (un-powered) wires. But many faults occur intermittently during an aircraft's flight, and are undetectable on the ground. These “no fault found” conditions are capable of bringing an aircraft down by causing a fire. In order to reduce the risk of these fires, arc fault circuit interrupters (AFCI) breakers have been developed and are being readied for large-scale implementation on aircraft power circuits. These breakers are designed to trip when a small arc occurs, dramatically reducing the risk of fire. The AFCI breaker can cause a maintenance enigma, however. Where traditional circuit breakers trip when damage to the wire is large and generally visible, the AFCI breakers trip when damage to wire is tiny and the wires are often otherwise fully functional. Finding this tiny damage can be difficult or impossible, especially where wiring is located in difficult to access areas.
Time domain reflectometry (TDR) has been used to analyze the path of signals in dead wires. However, when a system is active, such as an aircraft in flight, traditional TDR typically isn't used for active wiring having signals as the TDR signal and the wire signal can interfere with each other.